This invention relates to apparatus used for straightening electrode rod or bar assemblies which are bent during use in the electrolytic production of metal. More particularly, it relates to apparatus for automatically straightening rod or bar assemblies having a structure attached to an end of a rod or bar which includes two or more stubs extending from such structure for making a connection with an electrode body.
In the electrolytic production of a metal such as aluminum, for example, electric current is passed through a molten salt bath held in a container called a pot or a cell. The molten bath includes dissolved aluminum oxide, and the current passing through the bath reduces the aluminum oxide to aluminum which is collected on the bottom of the cell. Typically, the anode used in such a process is a carbon body connected to a metal rod or bar or connected to a rod or bar assembly having a structure on the end of a rod or bar. Whether the carbon body is connected directly to the rod or bar or to stubs on a structure on the end of a rod or bar generally depends on the size of the body. It is also noted that whether a rod or bar is used is a matter of choice, and the words "rod" or "bar" may be substituted one for the other in the following description of the invention and the accompanying claims. The free end of the rod is connected to a power source and the carbon body is suspended in the molten salt bath. During the course of producing aluminum, the carbon body is consumed and must be replaced from time to time. When the bulk of the body has been consumed, a relatively small portion remains, which is called a butt, and the rod with the butt thereon is removed from the cell and replaced with a rod having a new carbon body thereon. It is desirable to strip the butt from the rod and salvage the carbon for use in making a new anode body and to reuse the rod to make a new anode assembly.
The structure and size of the rod portion of the assembly vary with the size of the cell and the anode body suspended therein. In the early days of commercially producing aluminum, the rod was simply a straight length of copper with an end embedded in the carbon block. With the advent of expanded use of aluminum and greater production demands, cells grew in size as did the size of the carbon blocks. As a consequence, the metal suspension rods have become heavier and have been adapted for effecting a more stable attachment to a carbon block than offered by embedment in a single opening. One type of anode rod in common usage today features a straight length of aluminum bar having a yoke-like structure attached to an end. The yoke is made of steel and has a pair of arms extending outwardly in radially opposing directions from a cylindrical stub member. Another cylindrical stub member is connected to the end of each arm to complete the yoke, and it is attached to the end of the bar, preferably by friction welding the center stub to the bar end. The yoked bar is then attached to the carbon block by positioning the outer stubs in slightly oversize holes in the block and filling the space between the stubs and block with molten iron to embed and retain the stubs in the holes when it solidifies. Whether the rod is simply a straight length or a yoked bar assembly, as just described, it is likely to become bent at least to some degree during usage and require straightening before being reused. An unyoked bar tends to become bent slightly above its point of embedment in the anode block when it is removed from the cell. A yoked bar will typically become bent near the connection with the center stub and, in addition, the outer stubs tend to toe inwardly due to the differences in coefficients of expansion between carbon and steel. Whether the bar is yoked or not, it must be straightened before reuse to insure that the anode block can be properly placed in the cell.
Apparatus is known to automatically straighten a length of unyoked rod. Apparatus of this kind comprises opposing power actuated clamping jaws connected to a frame. The rods are suspended from an overhead transport system which passes through the frame. The apparatus is adapted to stop a suspended rod at the proper point with respect to the jaws. One set of jaws is then actuated to straighten the rod in a direction normal to the line of travel of the suspended rod, and then the other set of jaws is actuated to straighten the rod in the direction of line of travel to complete straightening the rod.
Apparatus for automatically straightening a yoked rod and removing toe-in from the stubs has not been known, however. Heretofore, such a rod has been straightened by manual manipulation in a powered press, and toe-in of the stubs has not been removed. Such straightening procedures have been time-consuming and expensive. To allow for stub toe-in that occurs through use, a rod assembly, when first made, is made with the stubs toed outward the maximum amount acceptable to assemble with an anode block. With each successive use, the stubs toe-in an additional amount until the toe-in exceeds an amount which permits assembly with an anode block. When that amount of toe-in occurs, the rod assembly is restubbed.